Interactions between motor commands and somatic perception in sensorimotor cortex

Current Opinion in Neurobiology

Volumn 6, Issue 6, 1996, Pages 801-810

  Nelson, Randall J ^a  

^a UNIVERSITY OF TENNESSEE HEALTH SCIENCE CENTER   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

BODY MOVEMENT; FACILITATION; HUMAN; LOCOMOTION; PERCEPTION; PRIORITY JOURNAL; REVIEW; SENSATION; SENSORIMOTOR CORTEX;

EID: 0030469339     PISSN: 09594388     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0959-4388(96)80031-6     Document Type: Article

References (80)

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14. Crammond DJ, Kalaska JF: Differential relation of discharge in primary motor cortex and premotor cortex to movements versus actively maintained postures during a reaching task. Exp Brain Res 1996, 108:45-61. The results obtained from recordings made in the PM and Ml of monkeys suggest that phasic bursts of PM activity occur mostly before movements but not when postural adjustments are made. Ml activity is about equal for both. These findings suggest a major role for the PM in selecting and planning visually guided movements. The discussion includes an extremely well focused evaluation of some current models of motor control. The authors suggest that Ml is not functionally homogeneous, but that it is part of a larger rostrocaudal precentral cortical motor control gradient within which multiple aspects of limb movements are processed in parallel. See [17] for evidence from imaging studies that several cortical sites are active during the same movement.
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26. Lebedev MA, Nelson RJ: Rhythmically firing (20-50Hz) neurons in monkey primary somatosensory cortex: activity patterns during initiation of vibratory-cued hand movements. J Comput Neurosci 1995, 2:313-334. Rhythmic activity of presumptive SI interneurons is complementary to quickly adapting SI neurons [60] recorded in monkeys performing vibratory-triggered wrist movements. A model is provided in which phasic and tonic interneurons are involved in tonically inhibiting the output of SI neurons. This model assumes that SI receives direct excitatory inputs from other regions related to changes in phases of behavioral tasks. The input to the circuit proposed was suggested to be from subcortical sources. However, cortico-cortical inputs with similar characteristics, such as those from Ml and PA, could provide the necessary input to result in task phase dependent modulation of sensory responsiveness.
27. Lebedev MA, Nelson RJ: High-frequency vibratory sensitive neurons in monkey primary somatosensory cortex: entrained and nonentrained responses to vibration during the performance of vibratory-cued hand movements. Exp Brain Res 1996, 111:313-325. These authors describe monkey SI neurons that fire preferentially to higher frequency stimuli. About half of these neurons decreased firing before movement if peripheral vibratory stimuli were sustained until after movements began. When vibration was not present, the vast majority showed premovement activity increases. This result suggests that although vibratory stimuli activate these neurons, their activity is suppressed before movements.
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31. These authors present evidence that the activity of groups of monkey SI neurons can represent the direction of moving tactile stimuli. The magnitude of the population vector varies with stimulus speed. The results suggest that there are dynamically maintained internal representations of the sensory environment that are necessary for higher-order processing.
32. Kalaska JF, Crammond DJ: Deciding not to go: neuronal correlates of response selection in a go/nogo task in primate premotor and parietal cortex. Cereb Cortex 1995, 5:410-428. The authors make several extremely important observations based on their recordings from area 5 in monkeys taught to execute or withhold movements in an instructed delay task. They hypothesize that part of the PA processes somatic and visual information about the location and environmental conditions of behaviorally salient body parts. They suggest that representations of motor responses to external cues reside in PA, whereas representations of intended movements are located in PM. They also suggest that these representations may be accessed when it is necessary to consult centrally generated corollary discharges "...to interpret the re-afferent input from the limb as movement unfolds." As is typical of these authors, the discussion is thorough, detailed, and extremely thought-provoking.
33. Colby LC, Duhamel JR, Goldberg ME: Oculocentric spatial representation in parietal cortex. Cereb Cortex 1995, 5:470-481. The monkey lateral intraparietal (LIP) cortex undergoes anticipatory remapping, allowing neurons to respond to visual stimuli even before a saccade is made to bring the stimulus into the neuron's receptive field. They also respond to the memory trace of recently flashed stimuli when saccades are made to the location where the stimulus had been. Thus, internal representations of impending movements and remembered stimuli shape LIP neuronal responses. It is probable that the same types of mechanism are functioning in the more somatic sensory part of the PA [31].
34. Biolac B, Burbaud P, Varoqueaux D: Activity of area 5 neurons in monkeys during arm movements: effects of dentate nucleus lesion and motor cortex ablation. Neurose! Lett 1995, 192:189-192.
35. Forss N, Jousmäki V, Hari R: Interaction between afferent input from fingers in human somatosensory cortex Brain Res 1995, 685:68-76. Using a 122-channel magnetometer, these authors recorded somatosensory evoked magnetic fields resulting from expected and intermittent stimuli. Their findings suggest that, in agreement with animal experiments [19], the different excitatory/inhibitory balances are maintained in sensorimotor cortices. This study illustrates the vast potential of this technique because its spatial and temporal resolution is better than other non-invasive methods of recording human evoked potentials. (See also [56].)
36. Paus T, Petrides M, Evans AC, Meyer E: Role of the human anterior cingulate cortex in the control of oculomotor, manual, and speech responses: a positron emission tomography study. J Neurophysiol 1993, 70:453-469.
37. Sadato N, Ibanez V, Deiber MP, Campbell G, Leonardo M, Hallen M: Frequency-dependent changes of regional cerebral blood flow during finger movements. J Cereb Blood Flow Metab 1996, 16:23-33. This study describes rCBF measurements made while subjects performed finger movements at various rates. The SMA and anterior cingulate cortex display the highest activation at slow rates and a decrease with faster movements. In general, the opposite is true for SI. The authors suggest that these changes in activation reflect progressive changes in performance from reactive to predictive modes. There is an intriguing possibility suggested here, although not directly by the authors. The opposite activation patterns of the SMA and SI and the postulated roles of SMA in response selection and motor inhibition [10") suggest that the SMA could be involved in modulating activity in SI. It is difficult to reconcile these observations with the hypothesis of suppression of sensation during predictive movements, however, unless it is assumed that increased SI rCBF represents increased suppression of inputs.
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60. Nicolelis MA, Baccala LA, Lin RC, Chapin JK: Sensorimotor encoding by synchronous neural ensemble activity at multiple levels of the somatosensory system. Science 1995, 268:1353-1358. The major findings of this paper are mentioned in the text of this review. The importance of simultaneous electrophysiological recording at several sites in a pathway cannot be stressed too much. The technical advances that this paper outlines will lead to answers about how distributed networks function in real-time during behavior. In this manner, questions of relative timing of effects at multiple cortical and subcortical locations can be directly answered. Moreover, synchronous activity in spatially separated populations of neurons, which waxes and wanes depending upon behavior contingencies, can be demonstrated.
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